Industrial contact dermatitis is an important occupational problem that causes much suffering for the afflicted employee and results in loss of productivity for the employer. It is a skin rash that develops from exposure to irritants, such as alkaline detergents or acids, or from exposure to "sensitizing" allergens, such as nickel, poison ivy, or antibiotics. Exposure to the irritants causes lesions that are similar to thermal burns. Exposure to the sensitizing allergens causes an allergic skin reaction that produces redness, swelling and itching. The first contact with such an allergen produces no visible skin reaction, but stimulates certain lymphocytes in a sensitive person to undergo an immunologic change. Upon subsequent exposure to the allergen, these sensitized lymphocytes release irritating substances that produce an inflammatory response in the skin (i.e. redness, swelling and itching). Continued, repeated exposure to these allergens causes the allergic reaction to be more acute and the dermatitis to become more severe.
Both types of dermatitis (irritant and allergic) result in redness, cracking, drying, scaling and blistering of the skin. Some relief of these symptoms is provided by applying soothing or drying lotions to the affected area. Also, topical corticosteroid preparations (which prevent the inflammatory response) may also provide relief. These steroid preparations are not without side effects, however, and should not be used routinely. Accordingly, the only truly effective treatment for contact dermatitis is further avoidance of the causative irritants or allergens. Obviously, therefore, the best cure is avoiding the initial contact with the irritants and/or allergens, i.e. prevention of the condition before it starts.
This goal may be achieved, at least in part, through the application of so-called "barrier creams" that form thin protective coatings on the skin's surface. There are different kinds of barrier creams, each offering protection against a specific class of irritants or allergens.
For example, for protection against powders, dust, dry soils, and highly viscous oils or tars, in which particles lodge in the pores of the skin, creams of oil-in-water emulsions containing inert fillers that protect the pores are used.
For protection against water-based irritants, hydrophobic films prepared from paraffins (petrolatum or beeswax) and/or silicones are used. Many of these hydrophobic films, being water-repellant, permit little, if any, evaporation of sweat from the skin. Accordingly, perspiration can accumulate between the protective film and the skin, thereby loosening the film and reducing its effectiveness. Also, because these hydrophobic films are nonpolar, they have little affinity for the skin, and thus adhere rather poorly to it.
The hydrophobic films can be supplied with emulsifiers to improve skin adhesion and to allow skin respiration. These additives, however, reduce the water repellancy of the film (which is the mode of action of these films), and hence, reduce its effectiveness as a barrier against water-based irritants.
Against organic or oil-based irritants (e.g. acetone, benzene, toluene, alcohol, turpentine, kerosene), hydrophilic substances such as polyethyleneglycols, polyacrylate, starch, gelatin, cellulose ether, or gum tragacanth are used. Also, soap surfactants such as triethanolamine or sodium alginate are used. These films are hydrophilic, and do not inhibit skin respiration. However, excess perspiration may wash off the barrier.
Most of the above films are soluble in either water or solvents, and are thus removed from the skin by washing, by perspiration, or through contact with solvents. Therefore, they require repeated application during a normal workday to ensure complete protection. Also, because of their specificity, they offer only limited overall protection against the wide variety of irritants commonly found in the workplace.